It depends on the brand, mostly, due to the flux and purity of copper used. The flux in braids is already dry, so it's not going to dry up further, however it also serves as a means of preserving the copper. The copper needs to remain free of tarnishing/oxidation so it's best to store the braid in a dry low oxygen environment (like an airtight jar). My techspray braid is still shiny and wicks well even though it was made sometime in the last decade.